1. Field of Technology
The present invention relates to a radio-controlled timepiece, an electronic device having a radio-controlled timepiece, a method of controlling a radio-controlled timepiece, and a reception control program for a radio-controlled timepiece.
2. Description of Related Art
Radio-controlled timepieces, which receive a standard time signal carrying time information, include timepieces that automatically unconditionally receive the standard time signal according to a predetermined schedule, and timepieces that detect movement of the timepiece and receive the standard time signal accordingly.
More specifically, Japanese Patent 3313215, for example, teaches a radio-controlled timepiece that detects if the timepiece is being worn or carried and receives the standard time signal while the radio-controlled timepiece is moving (see, for example, pages 5 to 7 and FIG. 1). This radio-controlled timepiece has a power conservation function that stops driving the timepiece when the timepiece is not being carried, and does not receive the standard time signal when the timepiece is not moving. When the timepiece detects a change from the not-worn (non-moving) mode to the worn (moving) mode and resumes the normal drive mode from the power conservation mode, the timepiece immediately forces reception of the standard time signal and corrects the displayed time. This radio-controlled timepiece can thus eliminate receiving the standard time signal when the radio-controlled timepiece is not being used, and thus reduce power consumption by the radio-controlled timepiece.
In addition, Japanese Unexamined Patent Application 2000-221284 teaches a radio-controlled timepiece that receives the standard time signal when the timepiece is not moving because reception is difficult when the timepiece is moving. This radio-controlled timepiece is used in an automobile, for example, and receives the radio signal when the vehicle ignition switch is off or the accessory switch is on. Stable signal reception may not be possible when the ignition switch is on due to interference from vehicle engine noise or because the vehicle is moving, but this radio-controlled timepiece improves reception stability by receiving the signal when the vehicle is stopped.
Japanese Unexamined Patent Appl. Pub. 2001-166071 teaches a radio-controlled timepiece that has a power generating means and prohibits receiving a radio signal while the power generating means is producing power. The generating means in this radio-controlled timepiece has a rotor, stator, and generating coil, and derives power by means of electromagnetic induction. The effects of electromagnetic noise produced when the generating means is producing power can interfere with normal signal reception when the generating means is producing power. However, by preventing signal reception while power is being generated by the generating means, this radio-controlled timepiece can correctly receive the standard time signal.
The radio-controlled timepiece that receives a signal while the timepiece is being worn must, however, be able to receive the signal while the timepiece is moving. However, while this radio-controlled timepiece can receive the standard time signal under certain circumstances while the timepiece is moving, the signal cannot be received if the timepiece moves to a location where the standard time signal cannot be received, for example. It therefore cannot be assumed that this radio-controlled timepiece can always reliably receive the standard time signal.
Furthermore, because the standard time signal is received and the time is adjusted when a change from a stationary to a moving state is detected, the power conservation mode is cancelled and the standard time signal is unconditionally received when the radio-controlled timepiece is picked up to be worn. However, reception may or may not succeed at this time depending upon the location where reception is attempted and the orientation of the bar antenna of the timepiece, and the correct time may not be displayed. If the signal cannot be correctly received at this time, the power supply of the radio-controlled timepiece is needlessly drained, and power conservation cannot be improved for the radio-controlled timepiece.
Another type of radio-controlled timepiece having a power conservation mode automatically receives and adjusts the time according to a predetermined schedule without driving the timekeeping mechanism when the power conservation mode is active. As a result, this radio-controlled timepiece can display the time relatively accurately even if signal reception fails after cancelling the power conservation mode because the standard time signal is received on a regular schedule even while the power conservation mode is active.
However, this type of radio-controlled timepiece consumes more power than the previous radio-controlled timepiece because the standard time signal is received even when the power conservation mode is active, and power consumption by the timepiece is not particularly reduced. Furthermore, if the radio-controlled timepiece is left in a location where the standard time signal cannot be received, this timepiece will automatically repeatedly attempt to receive the standard time signal at the scheduled reception time even while the power conservation mode is active, and power conservation by the radio-controlled timepiece cannot be improved.
Yet further, if the radio-controlled timepiece that receives the standard time signal when the timepiece is not moving is in an automobile and the automobile is not moving but the standard time signal cannot be correctly received because the vehicle is stopped in the midst of tall buildings, for example, standard time signal reception may succeed or fail even though reception is controlled based on detection of movement, and reliable reception therefore may not be assured. Improving power conservation in such radio-controlled timepieces may therefore not be possible in such timepieces because of such wasted attempts to receive the standard time signal.
The foregoing radio-controlled timepiece that prohibits reception while the generating means is producing power prohibits receiving the standard time signal while the timepiece is moving. The standard time signal is therefore normally received when the radio-controlled timepiece is not being worn. However, if the timepiece is located where standard time signal reception is poor, such as inside an office building, the timepiece may not be able to receive the time signal correctly. Such reception control cannot assure sufficient reception reliability and results in needless reception operations, and improved power conservation thus also cannot be provided with this type of radio-controlled timepiece.
The foregoing radio-controlled timepieces can thus receive the standard time signal while the timepiece is moving or can receive the standard time signal while the power conservation mode is active, and can thus successfully receive the standard time signal under certain circumstances. However, reception is not possible in some situations, such as when the radio-controlled timepiece is in a location where the standard time signal cannot reach, and these radio-controlled timepieces therefore lack sufficiently reliable signal reception. As a result, these radio-controlled timepieces consume much power when reception is attempted where the standard time signal cannot be received. Furthermore, because receiving the standard time signal consumes much more power than does simply driving the timekeeping mechanism, power consumption due to needless reception attempts is a particularly significant drawback.
An object of the present invention is therefore to provide a radio-controlled timepiece that can promote power conservation and improve the reliability of external signal reception. A further object of the invention is to provide an electronic device incorporating this radio-controlled timepiece, a control method for the radio-controlled timepiece, and a reception control program for the radio-controlled timepiece.